The present invention relates to automatic level setting of audio signals recorded on a magnetic tape according to the magnetic properties thereof.
The level of magnetically recorded signals is known to differ between magnetic tapes due to the differences in magnetic properties of the material of the tape. This would require the user to readjust the recording level whenever the tape is replaced.
Automatic level adjustment, shown and described in U.S. Pat. No. 4,220,979 assigned to the same assignee as the present invention, involves recording a test signal in a magnetic tape prior to the recording of audio signals and integrating the reproduced test signal to derive an average value of the amplitude of the test signal which reflects the magnetic properties of the tape. The average value of the test signal is checked against a reference to detect the difference between them to adjust the setting of a variable loss attenuator. Although the integration has the effect of smoothing insignificant variations of the reproduced signal to derive an accurate indication of the difference value, the occurrence of a drop-out would reduce the average value and hence an error would result.